Secure Communication Enabled by Time-Modulated Metasurface Antenna Based on Spread-Spectrum Technique

In cellular communication, several modulations have been proposed to ensure robust and secure communication, spread spectrum being one. This letter pursuits a new secure and cost-effective communication system by leveraging time-modulated metasurface antennas implementing the well-known concept spread spectrum. Recently, embedding and exploiting time-varying characteristics in electromagnetic devices can result in unique features. These features make it possible for antennas to be used for spread signal. For this purpose, we propose a time-modulated metasurface antenna operating within the microwave regime, where the metaradiators are time-modulated. Temporal changes in metaradiators expand the spectrum of the radiation signal of the antenna, similar to a noise-like spectrum with power spectral density very close to zero. In the same way as the spread-spectrum technique, carrier signals are spread when the temporal changes are biased by pseudorandom. The proposed system is theoretically and experimentally analyzed using a time-modulated metasurface antenna with 16 × 4 metaradiators. Our results have led to the emergence of a new class of antennas for secure communication in the microwave and cellular regimes, and it opens up a whole new world for research in this area.